A pharmaceutical injection device includes an injection needle mounting portion at its front end, a syringe mounting portion at its rear end for mounting thereon a syringe having a gasket, a plunger for pressing the gasket of the syringe mounted on the syringe mounting portion toward the injection needle mounting portion, a motor for driving the plunger, an encoder for detecting a rotation frequency of the motor, a controller connected to the encoder, and a memory connected to the controller.
Particularly, the plunger is driven by the motor to press the gasket toward the injection needle mounting portion, and then, the drug is injected through the injection needle into a human body, for example.
Meanwhile, the rotation frequency of the motor is detected by the encoder, and the injection amount of a drug is controlled so as to be a set amount. However, because of a considerable variation in part accuracy, it was difficult to perform a drug injection in a set injection amount.
In order to prevent this, one method has been proposed in which a relation between the rotation frequency detected by the encoder and the drug injection amount is stored in a memory, and the rotation frequency of the motor is controlled based on the data stored in the memory (See, patent Literature 1: Japanese Patent Publication JP2004-510505).